RCMP say Sawyer Robison is charged with second-degree murder in the killing of his uncle Bradford Clarke.
Clarke was found dead in his home near Killam where the two officers were shot.
Police searched for Robison after he was spotted leaving the scene.
He was arrested without incident three days later on a rural road.
Robison is in custody and is to appear in Wetaskiwin Court of Queen's Bench on Tuesday.